1. Technical Field
The present invention relates to an optical device and a projector.
2. Related Art
A projector which includes an optical device for modulating each of R, G, and B lights according to image information and combining the respective modulated color lights into image light, and a projection lens for expanding and projecting the image light thus formed is known (for example, see JP-A-2007-183396).
According to a projector disclosed in JP-A-2007-183396, an optical device includes three liquid crystal panels as reflection type optical modulation devices provided for each color light, three attachment members (support members) each of which has a triangle pole shape and a predetermined surface to which the corresponding liquid crystal panel is attached, and a cross dichroic prism which has a cube shape and combines the respective color lights modulated by the liquid crystal panels into image light. The three attachment members to which the liquid crystal panels are attached and the projection lens are disposed in the vicinity of the four side surfaces of the cube-shaped cross dichroic prism, respectively.
According to this type of projector, the respective liquid crystal panels are required to be disposed at the back focus position of the projection lens for producing clearer images. Moreover, pixel shifts between the liquid crystal panels need to be prevented for obtaining further clearer images. Thus, it is necessary to accurately perform focus adjustment for locating the liquid crystal panels precisely at the back focus position of the projection lens and alignment adjustment for aligning pixels of the respective liquid crystal panels at the time of manufacture of the optical device.
According to the projector disclosed in JP-A-2007-183396, the liquid crystal panels are attached to the attachment members via panel support plates, and thus structures for adjusting positions of the liquid crystal panels are provided between the attachment members and the panel support plates. More specifically, the positions of the liquid crystal panels are adjusted by shifting the liquid crystal panels relative to the attachment members fixed to the cross dichroic prism by using a jig.
In case of a projector which includes highly accurate reflection type liquid crystal panels, deterioration of projection images such as pixel shifts on and blurring of projection images is produced when only slight position shift of the liquid crystal panels is caused. Thus, it is preferable that the positions of the highly accurate reflection type liquid crystal panels are adjusted by using the projection lens practically used while the projection lens and the cross dichroic prism are combined by a head body having a lens support unit for supporting the projection lens and a pedestal on which the cross dichroic prism is mounted.
According to the projector disclosed in JP-A-2007-183396, for adjusting the positions of the liquid crystal panels by combining the projection lens and the cross dichroic prism by the head body, the lens support unit of the head body is disposed on the back side of the liquid crystal panels positioned in the vicinity of the projection lens. Thus, for the position adjustment of the liquid crystal panels, the jig needs to be inserted into a clearance between the lens support unit of the head body and the liquid crystal panels. In this case, the position adjustment of the liquid crystal panels becomes difficult.